I set a puzzle here every two weeks on a Monday. Send me your email if you want me to alert you each time I post a new one. Im always on the look-out for great puzzles. If you would like to suggest one, email me.

She was the only woman to have won the Fields medal, maths equivalent of the Nobel prize

The mathematician Maryam Mirzakhani died two weeks ago. Shewas 40. I had never heard of her before reading about her death in the papers. Its a piercingly sad story: Iranian-born, and latterly a professor at Stanford University, Mirzakhani was the only woman to have won the Fields medal, the equivalent for a mathematician of the Nobel prize, and is survived, in newspaper-speak, by a husband and a daughter.

I always find the locution survived by too cruel to bear. So final the rupture, no room for error: shes gone, theyre left. And, in this case, how young the mother and the wife.

It is a sad story for other reasons, too, not least the intensity of Mirzakhanis expression in the photograph most of the papers used. There is a beauty that can onlybe described as that of the minds migration to the face, the transfiguring beauty of exceptional intelligence. So its a double loss: thepremature loss of a person and the premature loss of her genius.

I remember there being an unspoken qualitative distinction atschool between those who were good at maths and science the priests of numbers and symbols and the more poetical of us, whose medium, as Wordsworth had it, was the language of men talking to men. The assumption, at least on the part of us Wordsworthians, was that creativity was all on our side. I have since come to think the word creative has much to answer for. Among the freedoms it sometimes gave us was the freedom from structure, knowledge and the obligation to convince.

Mirzakhani, it is said, considered being a writer before turning to mathematics. It is unlikely she believed shed made a choice in favour of an inferior, or less artistic, discipline. And she expressed her immersion in mathematics in language every writer will recognise like being lost in a jungle and trying to use all the knowledge you can gather to come up with some new tricks, and with luck you might find a way out.

The luck, of course, is no such thing. Its the mystery Keats called negative capability, the trust that the work will do itself if only we dareto plunge without irritability orinsistence into the dark, not sure we will find a way out at all. The bestwriting happens in this way, unintended, unknowing, grateful and surprised. Such abnegation of will is what we mean by creativity. So the mathematician and the artist are companioned in the same dark, and do obeisance to the same gods. The pity of Mirzakhanis death will be felt by poets as well as mathematicians.

2. Speaking of stars, guess how many miles (or km) the nearest star (after our Sun) to Earth is?

Like objects in your side-view mirror, stars in the night sky seem a lot closer than they are. Alpha Centauri is the closest ‘star system’ to us at an approximate distance of 4.37 light-years which works out to roughly 25 trillion miles or 40 trillion km away. ðŸ˜³

3. Alaska is simultaneously the most northern, the most western, and the most eastern state in the US

Wait, what? Look on a map and it’s easy to see that Alaska is the United States’ most northern and western state. But eastern? That’s because the Aleutian Islands are part of Alaska and stretch beyond the 180Â° line of longitude (which is measured from Greenwich) thus placing some of the islands technically in the Eastern hemisphere, since the dividing line for the eastern/western hemisphere is at 180Â° (source)

4. ‘Oxymoron’ is an oxymoron

The term was first recorded as latinized Greek oxymÅrum and is derived from the Greek where ‘oxys’ means “sharp, keen, pointed” and ‘moros’ means “dull, stupid, foolish”. Oxymoron is also an autological word, which means it expresses a property that is also possesses (e.g. the word “noun” is a noun, “English” is English, “pentasyllabic” has five syllables, and “word” is a word) [source]

5. If you start counting at one and spell out the numbers as you go, you won’t use the letter “A” until you reach 1,000

6. Oxford University is (way) Older than the Aztec Empire

Older, like it’s not even close. As the oldest university in the English-speaking world, Oxford is a unique and historic institution. While there is no clear date of foundation, teaching existed at Oxford in some form in 1096 and developed rapidly from 1167, when Henry II banned English students from attending the University of Paris. [source]

7. The official animal of Scotland is… the Unicorn

Royal Coat of Arms of the Kingdom of Scotland used from the 12th century to 1603

According to The Scotsman: in Celtic mythology, the Unicorn of Scotland symbolized innocence and purity, healing powers, joy and even life itself, and was also seen as a symbol of masculinity and power. It has been a Scottish heraldic symbol since the 12th century and today, the Royal Coat of Arms of the United Kingdom of Great Britain and Northern Ireland still has the English lion on the left and the Scottish unicorn on the right. [source]

8. There was a third Apple co-founder, Ronald Wayne. He sold his 10% stake for $800 in 1976. Today it would be worth roughly $75.5 billion

Ronald Wayne worked with Steve Jobs at Atari before he, Jobs, and Wozniak founded Apple Computer on April 1, 1976. Serving as the venture’s “adult supervision”, Wayne drew the first Apple logo, wrote the three men’s original partnership agreement, and wrote the Apple I manual.

Wayne received a 10% stake in Apple. Less than two weeks later, on April 12, 1976 he relinquished his equity for US$800. Legally, all members of a partnership are personally responsible for any debts incurred by any partner; unlike Jobs and Wozniak, then 21 and 25, Wayne had personal assets that potential creditors could seize. The failure of a slot machine company, which he had started five years earlier also contributed to his decision to exit the partnership.

Later in 1976, venture capitalist Arthur Rock and Mike Markkula helped develop an Apple business plan and converted the partnership to a corporation. A year after leaving Apple, Wayne received $1,500 for his agreement to forfeit any claims against the new company. [source]

9. With just 70 people, there is a 99.9% chance that two people share the same birthday

23 people is all it takes for there to be a 50/50 chance that two of the people share a birthday. The ‘birthday paradox‘ provides a valuable lesson in probability and reveals our tendency to think linearly instead of exponentially.

You can find a thorough mathematical explanation of the birthday paradox here, but at it’s core, we tend to think of our birthday compared to the 22 other people so there are 22 chances. But when all 23 birthdays are compared against each other, it makes for much more than 22 comparisons.

So the first person has 22 comparisons to make, but the second person was already compared to the first person, so there are only 21 comparisons to make. The third person then has 20 comparisons, the fourth person has 19 and so on. If you add up all possible comparisons (22 + 21 + 20 + 19 + â€¦ +1) the sum is 253 comparisons, or combinations. Check out the table below to see how the probability increases as the number of people do. [source]

The following table shows the probability for some other values of n (this table ignores the existence of leap years, as described above, as well as assuming that each birthday is equally likely)

10. There’s enough water in Lake Superior to cover North and South America in a foot of water

To talk of Lake Superior is to talk in superlatives. Its 3 quadrillion gallons are enough to cover both North and South America under a foot of water; it holds 10% of the world’s surface fresh water supply; at 31,700 square miles (82,100 sq km) it’s roughly the size of Maine.

If all 7 billion people on Earth drank a gallon of water per day it would collectively take us 1,174 years to drain it. [source]

If you want to email me your answer, or post it on Twitter with the hashtag #MondayPuzzle, Ill send the author of my favourite image a copy of my puzzle book Can You Solve My Problems?

Ill be back at 5pm UK time with the solution.

I set a puzzle here every two weeks on a Monday. Send me your email if you want me to alert you each time I post a new one. Im always on the look-out for great puzzles. If you would like to suggest one, email me.

Mirzakhani, who had breast cancer, died on Saturday, the university said. It did not indicate where she died.

In 2014, Mirzakhani was one of four winners of the Fields medal, which is presented every four years and is considered the mathematics equivalent of the Nobel prize. She was named for her work on complex geometry and dynamic systems.

Mastering these approaches allowed Mirzakhani to pursue her fascination for describing the geometric and dynamic complexities of curved surfaces spheres, doughnut shapes and even amoebas in as great detail as possible.

Her work had implications in fields ranging from cryptography to the theoretical physics of how the universe came to exist, the university said.

Mirzakhani was born in Tehran and studied there and at Harvard. She joined Stanford as a mathematics professor in 2008. Irans president, Hassan Rouhani, issued a statement praising Mirzakhani.

The grievous passing of Maryam Mirzakhani, the eminent Iranian and world-renowned mathematician, is very much heart-rending, Rouhani said in a message that was reported by the Tehran Times.

Irans foreign minister, Mohammad Javad Zarif, said her death pained all Iranians, the newspaper reported.

The news of young Iranian genius and math professor Maryam Mirzakhanis passing has brought a deep pang of sorrow to me and all Iranians who are proud of their eminent and distinguished scientists, Zarif posted in Farsi on his Instagram account.

I do offer my heartfelt condolences upon the passing of this lady scientist to all Iranians worldwide, her grieving family and the scientific community.

Mirzakhani originally dreamed of becoming a writer but then shifted to mathematics. When she was working, she would doodle on sheets of paper and scribble formulas on the edges of her drawings, leading her daughter to describe the work as painting, the Stanford statement said.

Mirzakhani once described her work as like being lost in a jungle and trying to use all the knowledge that you can gather to come up with some new tricks, and with some luck you might find a way out.

Stanford president Marc Tessier-Lavigne said Mirzakhani was a brilliant theorist who made enduring contributions and inspired thousands of women to pursue math and science.

Mirzakhani is survived by her husband, Jan Vondrk, and daughter, Anahita.

The missing square puzzle is an optical illusion used in mathematics classes to help students reason about geometrical figures; or rather to teach them not to reason using figures, but to use only textual descriptions and the axioms of geometry.

It depicts two arrangements made of similar shapes in slightly different configurations. Each apparently forms a 13Ã—5 right-angled triangle, but one has a 1Ã—1 hole in it. [source]

The key to the puzzle is the fact that neither of the 13Ã—5 “triangles” is truly a triangle, because what appears to be the hypotenuse is bent. In other words, the “hypotenuse” does not maintain a consistent slope, even though it may appear that way to the human eye. [source]

According to Martin Gardner, this particular puzzle was invented by a New York City amateur magician, Paul Curry, in 1953. However, the principle of a dissection paradox has been known since the start of the 16th century. [source]

Todays puzzle requires you to demonstrate superior intelligence to a contrary cat.

A straight corridor has 7 doors along one side. Behind one of the doors sits a cat. Your mission is to find the cat by opening the correct door. Each day you can open only one door. If the cat is there, you win. You are officially smarter than a cat. If the cat is not there, the door closes, and you must wait until the next day before you can open a door again.

If the cat was always to sit behind the same door, you would be able to find it in at most seven days, by opening each door in turn. But this mischievous moggy is restless. Every night it moves one door either to the left or to the right.

I set a puzzle here every two weeks on a Monday. Send me your email if you want me to alert you each time I post a new one. Im always on the look-out for great puzzles. If you would like to suggest one, email me.

The most famous theorem in maths is named after the Greek thinker Pythagoras. So is the most famous recreational mathematics publication in the Netherlands.

Pythagoras Magazinewas founded in 1961, and to celebrate its half century it recently published a selection of its best brainteasers in English. Ive selected three of them here, in increasing order of difficulty.

1) Dollar bills. In a bag are 26 bills. If you take out 20 bills from the bag at random, you have at least one 1-dollar bill, two 2-dollar bills, and five 5-dollar bills. How much money was in the bag?

2) Yin and Yang. The Yin-Yang symbol is based on the figure below, bordered by three semi-circles. How can you divide this shape into two identical shapes?

Big yin

3) Huge pie. A huge pie is divided among 100 guests. The first guest gets 1% of the pie. The second guest gets 2% of the remaining part. The third guest gets 3% of the rest, etc. The last guest gets 100% of the last part. Who gets the biggest piece?

Ill be back later today with the solutions.

NO SPOILERS PLEASE

I set a puzzle here every two weeks on a Monday. Send me your email if you want me to alert you each time I post a new one. Im always on the look-out for great puzzles. If you would like to suggest one, email me.

Football School, which I which I co-wrote with Ben Lyttleton, is a book for 7 to 13-year olds children that uses football to explain subjects like English, maths, physics, geography, philosophy and zoology. You (by which I mean any 7-13-year-olds you may know) can check out the Football School YouTube channel, in which Ben and I answer all questions about football and life. Submit your questions and subscribe!

For todays puzzle, let me introduce you to the Menger sponge, a fascinating object first described by the Austrian mathematician Karl Menger in 1926. Well get to the problem as soon as I explain what the object is.

The Menger sponge is a cube with smaller cubes extracted from it, and is constructed as follows: Step A: Take a cube. Step B: Divide it into 27 smaller subcubes, so it looks just like a Rubiks cube.

Please forgive me, though, for posing this toughie. The answer is jaw-droppingly amazing. In fact, I was told about the Menger slice by a respected geometer who told me it gave him probably his biggest wow moment in maths. Come back at 5pm BST and see for yourself.

I set a puzzle here every two weeks on a Monday. Send me your email if you want me to alert you each time I post a new one.

Im always on the look-out for great puzzles. If you would like to suggest one, email me.

* Here are a couple. 1) Each time you follow the iteration described in steps A to C you decrease the volume of the sponge, but increase its surface area. After an infinite number of iterations, you will have removed an infinite number of cubes. The sponge will then have zero volume and infinite surface area. 2) After an infinite number of iterations, the object is a fractal, that is, it contains parts that are identical to the whole thing.

Mathematical analysis reveals that for players with good control, using an unorthodox underarm technique gives better odds of scoring

It might invite ridicule, but it gets results. A scientific analysis has concluded that using a granny style underarm technique is the optimal way to take a free throw in basketball.

Adopting the unorthodox strategy could result in marginal gains for professional players, the research suggests. And, as sporting doctrine goes, marginal gains can lead to remarkable results.

Madhusudhan Venkadesan, who led the work at Yale University, said: Our mathematical analysis shows that if the thrower is capable of controlling the release angle and speed well, the underarm throw is slightly better for a basketball free throw.

However, it remains to be seen whether science will prove more persuasive than professional advocates of the underarm style.

The retired NBA player Rick Barry, a pioneer of the underarm free throw, was one of the most effective shooters of all time and when he retired in 1980 his 90% free throw record ranked first in NBA history. But he struggled to convince his teammates due to the inescapable fact that shooting underarm makes you look like a sissy, Barry said.

Venkadesan acknowledges that it is a difficult case to make.

One suspects there are social and cultural reasons you dont see that practised too often, he said. So what if some call it the granny throw? What matters is that the ball goes through the hoop! Rick Barrys record does support the underarm throw.

The study, published in the journal Royal Society Open Science, considered the chances of the ball being on target, depending on the style, speed and accuracy of a throw.

It found that if the player is capable of controlling the release angle and speed well, the underarm throw has slightly better odds of going in. But for amateurs who have only crude control, the release of the ball overarm is safer, sparing casual players the dilemma of choosing style or results.

An important factor in comparing the two strategies was how the ball approaches its target. When the ball approaches the net from directly above, as in a typical underarm throw, the cross-section of the target is large from the balls vantage point. This is good, as it means that if a throw is close to being exactly on target it has a very high chance of going in.

However, in trying to achieve this straight down entry, the amateur risks lobbing the ball extremely high due to their mediocre control. In this scenario, a small error in the timing of the release can cause the ball to grossly overshoot or undershoot the hoop.

So the overarm shot, where the ball sees a smaller cross-section of the hoop, but is less likely to go wildly off course, is a more conservative strategy.

This competition between the entry angle and speed underlies both the speed-accuracy trade-off and the relative accuracy of one style versus another, said Venkadesan.

For the professional player, the analysis predicts, this trade-off is finely balanced and probably within the margins of error of the model, which did not consider the backboard.

Barry, no doubt, would view the findings as confirmation of what he has argued all along. From the physics standpoint, its a much better way to shoot, he told the author Malcolm Gladwell in a recent interview. You have a little bit more margin for error than when you shoot overhand.